[jira] [Updated] (CALCITE-4522) Sort cost should account for the number of columns in collation

["hqx (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-4522?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

hqx updated CALCITE-4522:
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    Summary: Sort cost should account for the number of columns in collation  (was: Sort operator returns the same cpu cost no matter the RelCollation is empty or not)

> Sort cost should account for the number of columns in collation
> ---------------------------------------------------------------
>
>                 Key: CALCITE-4522
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4522
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: hqx
>            Priority: Minor
>              Labels: pull-request-available
>          Time Spent: 9h
>  Remaining Estimate: 0h
>
> The old method to compute the cost of sort has some problem.
>  # When the RelCollation is empty, there is no need to sort, but it still compute the cpu cost of sort.
>  # use n * log\(n) * row_byte to estimate the cpu cost may be inaccurate, where n means the output row count of the sort operator, and row_byte means the average bytes of one row .
> Instead, I give follow suggestion.
>  # the cpu cost is zero if the RelCollation is empty.
>  # let heap_size be min\(offset + output_count, input_count), and use input_count * log\(heap_size)* row_byte to compute the cpu cost.
> When fetch is zero, I found the output_count is 1 not 0. This conveniently ensure the log\(heap_size) no less than zero



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